Process for recovering dimethylnaphthalenes from cracked gas oil by combined solvent extraction and azeotropic distillation



March 2, 1

965 R. WYNKOOP ETAL 7 PROCESS FOR RECOVERING DIMETHYLNAPHTHALENES FROM CRACKED Filed July 17. 1961 GAS OIL. BY COMBINED SOLVENT EXTRACTION AND AZEOTROPIC DISTILLATION 8 Sheets-Sheet 2 d. E 0 p.

' I l I l I DEG 0 20 C 40 6O 80 I00 OMN mo 80 6O 4O 20 0 d E 0 0- 26m I I T' --|r-1- DEG 0 2 4 6 96 98 I00 C60 IOO 9a Wt RAYMOND WWCB'F JOSEPH a ALLEN BY Wan A TORNEY March 2, 1965 R. WYNKOOP ETAL 3,171,863

PROCESS FOR RECOVERING DIMETHYLNAPHTI'IALENES FROM CRACKED GAS OIL BY COMBINED SOLVENT EXTRACTION AND AZEOTROPIC DISTILLATION Filed July 17, 1961 8 Sheets-Sheet 3 DEG Extract l'n terpolo ted Tue Lines 0, o

I Rcffino e DMN INVENTORS Wilda A TORNEY March 1965 R. WYNKOOP ETAL 3,171,863

PROCESS FOR RECOVERING DIMETHYLNAPHTI'MLENES FROM CRACKED GAS OIL BY COMBINED SOLVENT EXTRACTION AND AZEOTROPIC DISTILLATIQN Filed July 17, 1961 8 Sheets-Sheet 4 Ex roct o r Rclffinclfe Feed Point--- wi. DMN in Extract Phase N C I l O 20 4O 60 BO IOO Wt. DMN in Roffinote Phase INVENTORS RAYMOND WYNKOOP BY JOSEPH s. ALLEN Wi h A TORNEY March 2, 1965 R. WYNKOOP ETAL 3 6 PROCESS FOR RECOVERING DIMETHYLNAPHTl-IALENES FROM CRACKED v GAS OIL BY COMBINED SOLVENT EXTRACTION AND AZEOTROPIC DISTILLATION Filed July 17. 1961 8 Sheets-Sheet 5 DEG Extract lnterpolated Z:

Tie Lines ceo INVENTORS RAYMOND WYNKOOP BY JOSEPH G. ALLEN A TORNEY Roffinote l C m X E R. WYNKOOP EI'AL ,8

NG DIMETHYLNAPHTHALENES FROM CRACKED SOLVENT EXTRACTION 8 Sheets-Sheet 6 Feed Point AND AZEOTROPIC DISTILLATION GAS OIL BY COMBINED March 2, 1965 PROCESS FOR RECOVERI Filed July 17. 1961 INVENTORS M, ATTORNEY Wt-% DMN in Roffincne Phase RAYMOND WYNKOOP w? JOSEPH G. ALLEN Mamb 1965 R. WYNKOOP ETAL 3 ,8 3

PROCESS FOR RECOVERING DIMETHYLNAPHTI'ZALENES FROM CRACKED GAS OIL BY COMBINED SOLVENT EXTRACTION AND AZEOTROPIC DISTILLATIQN 8 Sheets-Sheet 7 Filed July 17. 1961 DEG interpolated Tie Lines DMN LIGHT GAS OIL mm RAYMOND K JOSEPH G. ALLEN M oremzvr Mgrch 2,

Filed Jfily 17. 1961 Solvent HG Wt. DMN in Extract Phase PROCESS FOR RECOVERING DIMETHYLNAPHTHALENES FROM CRACKED R. WYNKOOP ETAL 3, 71,863

GAS OIL BY COMBINED SOLVENT EXTRACTION AND AZEIOTROPIC DISTILLATION 8 Sheets-Sheet 8 Hg 9 s -Rcffinate c I I Wt.% DMN in Roffinate Phose INVENTORS RAYMOND WYNKOOP BY JOSEPH G.ALLEN A TORNEY United States Patent Ofiice 3,171,863 Patented Mar. 2, 1965 3,171,863 PROCESS FOR RECOVERING DIMETHYLNAPH- THALENES FRDM CRACKED GAS OIL BY COMBINED SOLVENT EXTRACTION AND AZEOTROPIC DISTILLATHON Raymond Wynkoop, Gladwyne, and Joseph G. Aiien,

Ridley Park, Pa., assignors to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey Filed July 17, 1961, Ser. No. 124,726 9 Claims. (Cl. 2.60-674) This invention relates to a process for segregating petroleum hydrocarbon mixtures into relatively aromatic and relatively non-aromatic fractions. It particularly relates to a method for separating from such mixtures dimethylnaphthalene concentrates. It especially relates to a process for recovering 2,6- and 2,7-dimethylnaphthalene from cracked gas oil by combined solvent extraction and azeotropic distillation with diethylene glycol.

The synthetic fiber market has achieved significant importance in the commercial world. One of the more important materials from which such fibers are made is the polyester of 2,6-dicarboxynaphthalene. Therefore, it is an object of this invention to produce an aromatic concentrate which is rich in 2,6-dimethylnaphthalene which is an intermediate for preparing the diester monomer. Specifically, the principal object or" this invention is to recover from cracked gas oil an aromatic concentrate composed almost entirely of 2,6- and 2,7-dimethylnaphthalene; The 2,6-isomer can be separated from the 2,7- isomer by, say, fractional crystallization. The process of this invention is economical and simple and it produces a dimethylnaphthalene concentrate from which the 2,6- isomer can be obtained in high purity.

The present invention is based on the discovery that under narrow conditions of temperature and solvent dosage the desired, say, 2,6- and 2,7-DMNs can be concentrated by, first, an extraction stage followed by an azeotropic distillation stage wherein both stages utilize a polyalkylene glycol such as diethylene glycol as the treating agent.

The charge material used in the present invention is obtained as a cracked gas oil fraction boiling in the range of 400 F. to 650 P. which contains alkyl naphthalene and dialkyl naphthalene constituents. Within this definition of starting material are included cracked gas oils as obtained directly from distillation of cracking products, such gas oils having an initial boiling point not substantially lower than 400 F. and a final boiling point not substantially higher than 650 F; mixed aromatic concentrates obtained from such cracked gas oils and having a boiling range substantially the same as the starting cracked gas oil; and fractions separated from either of the above materials but which boil Within the narrower range of 475 F. to 520 F, preferably between 480 F. and 515 F. As used herein, the term cracked includes thermal, catalytic, and reforming operations.

According to the present invention, the cracked petroleum fraction should contain substantial amounts of dicyclic aromatic compounds and preferably little if any tricyclic aromatic compounds. Since the pertoleurn fraction can be derived from practically any source of crude petroleum, its specific composition can vary considerably. Even though the boiling ran e of the petroleum fraction can be between 400 F. and 650 F., it is preferred that the boiling range be substantially between 475 F. and 520 F., more preferably between 480 F. and 515 F. v-ia distillation, so that a concentrate of such dicyclic compounds as dirnethylnaphthalenes (DMN) can be obtained. Furthermore, according to this invention, the material (eg. the extract) in contact with the solvent,

described hereinafter, during the azeotropic distillation step should have total aromatic content of at least 40% by weight, preferably at least 60% by weight. In fact, best results are obtained if this material is aromatic hydrocarbons. Further, the cracked fraction charged to the solvent extraction step should contain at least 23% by weight DMNs, preferably from 5% to 60% by weight DMN.

Additionally, suitable charge materials within the definition of cracked gas oils typically have an A.P.I. gravity at 60 F. between 12 and 40; a refractive index at 20 C. of from 1.4500 to 1.5800; and a sulfur content of from 0.05% by weight to 3.0% by weight.

The solvents utilized in the present process are those which are selective for aromatics and which are selective azeotrope formers with dialkylnaphthalene. Suitable solvents are the polyalkylene glycols, including, for example diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and mixed ethylene glycol-propylene glycol ethers. The preferred solvent which is both an extracting agent and an azeotroping agent is diethylene glycol (DEG).

The selectivity of the solvent can be enhanced to a considerable extent by the addition thereto of small amounts of water. For example, certain limited amounts of water, say, up to 20%, and preferably up to 10% by weight of the solvent composition will enhance the selectivity of the solvent between dicyclic aromatic and non-aromatic hydrocarbons. It has also been found that at least 0.25% water is needed in the solvent to effectively cause the DMNs to azeotrope with the solvent.

According to the present invention the temperature during the extracting stage can vary between 240 F. and 320 F. but the preferable range is from 260 F. and 310 F. Actually,, the dimethylnaphthalenes can be best extracted by diethylene glycol at a temperature of 275 The DMN-DEG azeotrope can be recovered over a temperature range of 448 F. and 460 F. However, if the desired DMNs are 2,6- and 2,7-dimethylnaphthalenes; then the DMNDEG azeotrope should be recovered over a temperature range of 451 F. to 454 F.

The solvent extraction step is performed by procedures known to those skilled in the art. For example, countercurrent extraction may be performed in a suitable column equipped with granular packing or equipped with a series of rotating discs. The solvent/feed ratios for extraction usually range from about 0.5 to 15 by volume. In addition, it has been found that the efiiciency of aromatic extraction by the solvent can be enhanced by recycling as reflux a portion of the dimethylnaphthalene concentrate recovered from the azeotropic distillation step. The DMN concentrate which is recycled as reflux should enter the extraction zone at a locus intermediate the feed and the extract.

The azeotropic distillation is ordinarily conducted at atmospheric pressure, but elevated or reduced pressures may be employed if desired. The solvent dosage for azeotroping should be at least 3 parts solvent per 2 parts hydrocarbon. An excess of solvent is desirable. Suitable solvent/hydrocarbon ratios ordinarily vary between about 1 to 10 but this factor may be varied in order to azeotrope only the dimethylnaphthalenes. The preferred solvent/ feed ratio range is 1.5 to 2.5: 1.

Thus, the present invention provides a process for recovering a dimethylnaphthalene concentrate from cracked gas oil which comprises contacting at a temperature between 240 F. and 320 F. in an extraction zone cracked gas oil feed containing dimethylnaphthalene and boiling substantially within the range of 475-520 F. with a solvent which is selective for aromatics and which is a selective azeotrope former with dialkylnaphthalenes; separating a raflinate phase rich in non-aromatic hydrocarbons and an extract phase enriched in dimethylnaphthalenes; subjecting the extract phase to azeotropic distillation; removing an overhead fraction consisting essentially of dirnethylnaphthalenes and solvent; recovering die methylnaphthalenes from the solvent; and removing a bottoms fraction consisting essentially of solvents and aromatics which azeotrope above said dimethylnaphthalenes.

FIGURE 1 is a diagrammatic representation for one manner of practicing the present invention.

FIGURE 2 is a plot of mutual soluble data contained in Table I for the system diethylene glycol-dimethylnaphthalene.

FIGURE 3 is a plot of the mutual solubility data contained in Table II for the system diethylene glycol-whole catalytic gas oil.

FIGURE 4 is a ternary diagram with conjugate line for the system whole catalytic gas oil-dimethylnaphthalene-diethylene glycol.

FIGURE 5 is a plot of solvent content vs. concentration for the ternary system of whole catalytic gas oildimethylnaphthalene-diethylene glycol. Also plotted as FIGURE 5 is a selectivity diagram for whole catalytic gas oil in this ternary system.

FIGURE 6 is a ternary diagram with conjugate line for the system 480-515 F. catalytic gas oil-dimethylnaphthalene-diethylene glycol.

FIGURE 7 is a plot of solvent content vs. concentration for the ternary system of 4805l5 F. catalytic gas oil-dimethylnaphthalene-diethylene glycol. Also plotted as FIGURE 7 is a selectivity diagram for the 480-515 F. catalytic gas oil fraction in this ternary system.

FIGURE 8 is a ternary diagram with conjugate line for the system light gas oil-dimethylnaphthalene-diethylene glycol.

FIGURE 9 is a plot of solvent content vs. concentration of the ternary system light gas oil-dimethylnaphthalene-diethylene glycol. Also plotted as FIGURE 9 is a selectivity diagram of a light gas oil fraction in this ternary system.

Reference is now made to the accompanying FIGURE 1 which is a schematic fiowsheet showing the principal apparatus for practicing one embodiment of the present invention.

The feedstock, hereinbefore described, is. charged through line 23 into solvent extraction tower 24 at a tem-v perature of about 275 F. The aqueous solvent, say, diethylene glycol containing about 2% water, is charged to the tower 24 through line 26. From line 25 is removed the predominately non-aromatic raflinate stream and the extract, enriched in dimethylnaphthalenes, is removed via line 27. Thus, the gas oil feed flows countercurrent to the diethylene glycol. In order to enhance the selectivity of the solvent for dimethylnaphthalenes and for aromatic hydrocarbons generally, a reflux stream of dimethylnaphthalene concentrate is charged to the tower via line 39. Make-up solvent may be added to the extraction zone through line 30.

The extract enters distillation tower wherefrom hydrocarbons which azeotrope below about 450 F. are removed via line 41. The heavier aromatic fraction comprising essentially concentrated dimethylnaphthalene plus the solvent is passed from tower 40 through line 42 into azeotropic distillation tower 28. The dimethylnaphthalene-DEG azeotrope which distills beginning at about 451 F. and ending at about 454 F. is removed via line 21. In this boiling range the DMN components are malnly the 2,6- and 2,7-isomers. If it is desired to obtain a dimethylnaphthalene product also containing the other isomers, the boiling range can be broadened to 44S460 F. Suitable reflux is returned through line 36 to control the reflux ratio between about 2 and 30. Preferablythe reflux ratio will be from about 3:1 to 5:1.. It has been 4 found that the composition of the DEG-DMN azeotrope in line 31 is 58% by weight DEG and 42% by weight DMN. The residuum aromatic hydrocarbons distilling above about, say, 454 F. are removed through line 29. In all cases, the DEG can be recovered and recycled to the process to effect economies in the operation.

The DEG-DMN azeotrope removed through line 31 can be further processed, such as by cooling to less than 100 F., in order to break the azeotrope into two phases, e.g., a DMN phase 33 and a DEG phase 34. The DMN is recovered by, say, decantation, from chill tank 32 land the recovered solvent is usually recycled to the process. Suitable reflux is added to tower'28 via line 36 and make-up solvent can be added through line 43.

A portion of the concentrate of 2,6- and 2,7-dimethylnaphthalene is recycled as reflux via line 39 to the extraction zone 24. A small portion of DMN concentrate is passed through line 38 and mixed with the separated DEG in line 36 in an amount sufficient to maintain the DEG- DMN azeotrope composition. The DMN product from line 35 can be further processed. For example, 2,6-DMN of purity can be recovered from the 2,7-DMN via fractional crystallization.

The following examples are cited to illustrate the features of the invention.

EXAMPLE I Table I.Mutual solubility data for system diethylene glycol-dimethylnaphthalene Weight Percent Solubility Temp, F.

DEG in DMN in DMN DE G 1 The dimethylnaphthalene was prepared by azeotropic distillation of a 480-515" F., aromatic fraction from CGO. GLPC analysis shows 23.3% non-DMN material.

Table Il.-Mutual solubility data for system diethylene glyc0lwh0le CG0 1 Analysis of the gas oil shows about 40% aromatics and 5.3 weight percent dimethylnaphthalene.

The above data are plotted in FIGURES 2 and 3. From the curves it is noted that 275 F. is a satisfactory operating temperature. The solubilities of DMN and DEG are high enough for practical processing and the solubilities of the C60 and DEG are low enough so as not to be competitive. In addition, the relative'solubilities do not change materially with temperature in this portion of the curves.

EXAMPLE II Once the operating temperature of 275 F. had been selected, mutual solubilities were run on various mixtures to determine the areas of single phase and two-phase comternary diagram. Each sample was formulated according to the indicated point composition and placed in an appropriate apparatus. The sample was heated to 275 F. and allowed time to reach equilibrium. The raflinate l T bl HI and extract phases were separated and Weighed. Weight posltlon, conventlofna l i' a e ratios for each phase were calculated from the results. isifimarizes the results or t e mixture cata ytic gas 01 The phases were analyzed first for diethylene glycol N/DEG' The sample was then partitioned between water and pentane to remove the DEG. The pentane was stripped Table lll MumglEmlublhty g CGO/DMN/ off and the hydrocarbon portion analyzed for dimethyl- G system at 7 napiithalenes. Finally, a material balance was made between the compositions of the starting phase and the Solute Solvent s bilii iii rafiinlate and extract i g 1 t Using all of the hereinabove data, the attached diagrams and following tables were constructed. The sin- DEG 5.3% DMN/94.7%CGO 2.8 gle conjugated line for interpolation of tie lines was g g- 888 28 plotted as recommended by Perry, Chemical Engineers DEG: 68277ZDMN/31I37Z coo 7Z4 Handbook, 3rd edition, at page 724. The interpolated gg g g gf g 3 i3 8 tie line data were used to calculate data for a Maloney 5.3% '15i\ii/i7i.'7%"(56o DEG "III" I 1.0 and Schubert Solvent Content-Concentration Diagram i333 838"" 3%" 2'}, and a Selectivity Diagram according to the method illus- 7217 7; Dim 273%; co III DEG: I 719 trated in Perry, supra, at pages 734-737. The minimum 85.5% DMN/14.5%CGO- D reflux ratio was determined for each system based on 90.0 DvrN 9.4 coo.- DEG 26.4 100% 2,G Dl\i[N DEG 27.0 obtaining a DMN concentrate of about 85% (a concentration less than the solutrope concentration).

A fraction boiling between 480-515 F. was distilled A. WHOLE CGO-DIMETHYLNAPHTHALENE- from the above whole catalytic gas oil and was admixed DIETHYLENE GLYCOL with dimethylnaphthalenes and diethyleneglycol for mu- 1 Composition f Components used in preparing the tual solubility studies. Table IV summarizes the results. bl d for miscibility and phase composition studies:

Table IV.-Mutual solubility data for 480515 F., CGO/ DMN/DEG system at 275 F. coo DMN Concentrate Wt. percent 1 Wt. Percent DMN 5.3 90.6 Solute Solvent 5 151 Wt. Percent Gas oil 94, 7 9, 4

47.77 DMN/52.37 CGO 2.7 72.87; Dim/27.2 7; CGO- 7.8 (2) FIGURE 4-Ternary Diagram with con ugate 86% DMN/ 94% 8 line for interpolation.

DEG 0.8 (3) FIGURE 5Selvent Content versus Concentragag $3 tion and Selectivity Diagram for Whole coo. DEG 10.8 (4) Table VIfiSummary of Phase Composition Data. ggg $32 5 Table VII-Analysis of Raffina-te and Extract DEG" 27.0 Phases.

0 (6) Table VIII-Data for construction of Selectivity Diagram and Solvent Content versus Concentration. A fraction boiling between 480-515 F. was distilled (7) Minimum Reflux to 1' from a residuum from thermally cracking a catalytic refl was admlxed 4 descnbed for Solu- Table VI.Summary of phase composition study of bility studies. Table V summaries the results. whole CGO/DMN/DEG System 5 Table V.Mutual solubility data for 4805J5 F. light 1 o aromatics fraction. /DMN/ DEG system at 275 F. Weight Percent Weight Percent,

Sample Solvent-Frce Basis Wt percent N0. Component Solute Solvent ssoiivtgnii P 1 R E I, R E

DEG 5.0% Dim/05.0% 00-0..... 4.6 DEG 13.8% DMN/86.2% OGO- 5. 2 45 9 3 DEG 26.5% DMN/73.5% CGO- 6.0 DEG 47.8% DMN/5i.2% 0G0. 7.6 m0 0 100 0 DEG 69.3% DMN/30.7% CGO 9. 9 DEG 90.6% DMN/9.4% CGO 15.0 26 7 1 DEG 100% 2,6DMN 13.0 5.0% DMN/95.0% CGO.. DEG 5.6

60.3% Dam/30.7% ooo-.. DEG 15.4 5 10M loo-0 90.6% Dim/0.4% oGo. DEG-.. 26.4 36 0 55 1 100% 2,6-DMN DEG 27.0 463 516 23.7 39.3 Tl 1 .s db d tilin a480-515F.fraetioniromlight aromiigir a g o ill hgii biropibalfy iiislling a DMN cut from it. The 0 0 fraction, 100% aromatic, represents a 4SO-515 F. fraction minus the dimethylnaplithalenes. percent DMNs.

Actual analysis by GLPG shows about 5 Wt.

EXAMPLE III To obtain tie line data for each system three points were selected from within the two-phase region of the P Composition of Starting Phase. R=Composition of Ratfinate Phase. E =Compositi0n of Extract Phase.

T able VII .Analysis of rafiinate and extract phases from whole CGO/DMN/DEG system at 275 F.

Raflmate Extract '7 7 Weight percent in- Totals Wt., t., Wt., Wt., Wt., gmS. Raffinate Extract percent gms. percent gms.

DMN 20. 4 12.0 4.1 1. s 13 8 DE G 2. 3 1. 4 92.2 40. 3 41. 7 GO 77. s 45. 3 3. 7 1. 6 46. 9 7 7 DMN 39. 1 22. 1 10. 6 4. 6 26. 7 5. 3. 1 86. 0 37. 5 40. 6 55. 4 31. 3 3. 4 1. 5 32. 8

T able' VIII.Data 1 for selectivity diagram and solvent content vs. concentration for whole CGO (1) 480-515 F. gas oil fraction was distilled from Extract Phase Extract Phase Rafiinate Phase #DE G/#HC Solvent-Free a DMN CGO DMN C GO DEG DHN CGO DMN Extract Rafi.

4. 1 3 7 52. 6 47. 4 2. 3 :4 77. 3 11. 8 023 10. 6 3 4 7,5. 7 24. 3 5. 5 39. 1 55. 4 6. 1 058 11. O 3 3 76. 9 23. 1 V 5. 6 55. 1 39. 3 6. O 059 1 O 100 2. 5 97. 5 99. 0 026 27 0 100 18. 0 82. 0 2. 7 220 INTERPOLATED TIE LINE DATA 73. 1 25. 4 1. 5 94. 4 5. 6 17. 3 2. O 97. 6 2. 4 2. 7 209 75. 0 22. 0 3. O 88. O 12. O 13. 8 10. 2 88. 2 11. 8 3. O 160 77. 5 19. 5 3. O 86. 7 13. 3 10. 3 20. O 77. 7 22. 3 3. 4 .115 79. 9 17. O 3. 1 8-1. 6 15. 4 7. 1 30. 4 67. 3 32. 7 4. 0 076 94. 3 2. 6 3. 1 45. 6 54. 4 3. O 83. 6 13. 8 86. 2 16. 5 031 97. O 1. 0 2. O 33. 3 66. 7 2. 6 .32. 3 V 5. 2 94. 8 32. 3 027 'A11 were weight percent.

3 CGQDIMETHYLNAPHTHALENE- TABLE IX .--Summary of phase composition study of DIETHYLENE GLKCOL 480.-5I5 F., CGO/DMN/DEG system at 275 F.

Weight Percent, Solvent-Free Basis the Whole gas oil at 50 theoretical plates and 50:1 refiUX ratio. I Sample Composition of components used in preparing the Compmlent blends for miscibility and phase composition studies: P

19.4 480515I. DMN 0011-. 39.9 0 G0 centrate 40. 7 100.0 Wt. Percent DMN a 24.7 90.6 Wt. Percent Gas Oil 75.3 9.4 28.0 39.7 32.2

(2) FIGURE 6Ternary Diagram with conjugate 100") line for interpolation. 3 (3) FIGURE 7Solvent Content versus Concentra- 23:5 tion and Selectivity Diagram for 480-515 F., CGO. 10M) (4) TABLE IXSummary of Phase Composition Data.

(5) TABLE XAnalysis of Raffinate and Extract Phases.

(6) TABLE XIData for construction of Selectivity Diagram and Solvent Content versus Concentration.

(7) Minimum Reflux Ratio-12 to 1.

P=Gomposition of Starting Phase. R=Composition of Raffinate Phase. E Composition of Extract Phase.

These data and miscibility data on the following table 7 were used in constructing the ternary diagram.

TABLE X.-Analysis f rafifinate and extract phases from 480515 F., CGO/DMN/DEG system at 275 F.

Baflinate Extract Weight percent in Sample Totals N 0. Component Wt.

Wt., Wt., Wt., W11, gms. Ralfmate Extract percent gmS. percent gms.

31. G 18. 3 2. 2 0. 9 19. 2 2. 6 1. 93. 1 37. R 39. 3 65. 8 38. 1 4. 7 1. 9 e0. 0

TABLE XI.-Data 1 for selectivity diagram and solvent content vs. concentration for 480515 F. CGO

Extract Phase Extract Phase Ealfinate Phase Raff. Phase #DEG '#HC Solvent-Free Solve11tFree Point N0.

DEG DMN CGO DMN CGO DEG DMN CGO DMN CGO Extract Rail.

INTERPOLATED TIE LINE DATA 1 All are weight percent.

C. 480-515" F. LIGHT GAS OIL-DIMETHYLNAPH- (6) TABLE X l V-Data for Construction of Selectivi- THALENE'DIETHYLENE GLYCOL ty Diagram and Solvent Content versus Concentration.

(1) The starting material is a plant distillate fraction (7) Minimum Reflux Ratio 51% DMN in charge, boiling between 400 550 F. The 400550 P. fraction 1 to Was dxsnned at 50 theoretlcal plates and 50:1 rfiflux T able XII.Summary of phase compositionstzidy 0 480- ratio into a 480515 F. cut. This fraction was 100% F ht D o aromatic and contained 51% dimethylnaphthalenes. The [lg gas MN/DEG System at 275 DMN concentrates used in all the studies were pre- 5 P3116111 by lazetitropiczdly distilling this fraction with di- SH 1 Weight Percent sw l e g e y.ene g yco p oven-wee asis Composition of components used in preparing the Component blends for miscibility and phase composition studies:

480*515. F DMN 4%.; 12.3 54 s 53. 0 67 3 Gas 011 Concentrate 43:3 510 452' 1713' "'52"? Wt percent DMN 5 0 6 100. 0 100. 0 100. 0 0 100. 0 100 0 Wt. percent Gas Oil 95.0 9.4 65 2915 33 4 3L6 56 8 2.4 88.2 .0 5.1 66 6 68.4 43 2 (2) FIGURE 8Ternary diagram With con ugate 1111c for interpolation. 100.0 100.0 100.0 100 0 100.0 100 0 (3) FIGURE 9fiSo1vent Content versus Concentra- 41.5 61.5 15.0 69 2 68.2 76 5 e e 40.0 9.8 80.4 gssnognd 1n Selectmty Diagram for 480 515 F. hght 1&5 2&7 L6 30 8 3L8 23 5 (4) TABLE XIISummary of Phase Composition 10M 10M 100-0 100-0 100-0 100 0 Data.

(5) TABLE XIII-Analysis of Raffinate and Extract P=comp sition Starting Phase- R=Composition of Raffinate Phase. P1111868. 7 5 E =C0mpositi0n of Extract Phase.

i tween 240 F. and 320 F. in an extraction zone cracked gas oil feed containing dimethylnaphthalenes and boiling substantially within the range of 400-650 F. with a polyalkylene glycol solvent which is selective for aromatics and which is a selective azeotrope former with dialkylnaphthalenes; separating a raffinate phase rich in nonaromatic hydrocarbons and an extract phase enriched in dimethylnaphthalenes; subjecting the extract phase to azeotropic distillation; removing an overhead fraction consisting essentially of dimethylnaphthalenes and solvent; recovering 2,6- and 2,7-dimethylnaphthalenes from the solvent; and removing a bottoms fraction consisting essentially of solvent and aromatics which azeotrope above said dirnethylnaphthalenes.

2. A process according to claim 1 wherein a portion of the recovered dimethylnaphthalenes are recycled as reflux to the extraction zone at a locus intermediate the feed and extract.

5 head fraction is removed at a temperature between 448 F. and 460 F.

7. A process according to claim 6 wherein a portion of the separated dimethylnaphthalenes are recycled as reflux to the extraction zone at a locus intermediate the feed and extract.

8. A process for recovering an aromatic concentrate composed of 2,6- and 2,7-dimethylnaphthalenes from catalytic gas oil containing 2,6- and 2,7-dimethylnaphthalene which comprises distilling said gas oil to obtain a hydrocarbon fraction boiling within the range of 480 F. to 515 F; contacting said fraction in an extraction zone at a temperature between 260 F. and 310 F. with aqueous diethylene glycol solvent; separating a rafiinate phase rich in non-aromatic hydrocarbons and extract phase enriched in dimethylnaphthalenes and containing at least 60% total aromatic hydrocarbons in the extract contained therein; subjecting the extract phase to fractionation; removing the hydrocarbons azeotroping below 450 F; removing a bottoms product containing solvent; subjecting the product to azeotropic distillation; removing overhead a hydrocarbon-solvent mixture azeotroping between 451 F. and 454 F.; cooling said azeotropic mixtune to break the mixture into a solvent phase and a 2,6- and 2,7-dimethylnaphthalene phase; recovering said dimethylnaphthalenes from the solvent; removing a residuum distilling above 454 F.; and recycling a portion of the separated dimethylnaphthalenes to the extraction zone at a locus intermediate said fraction and extract.

9. A process according to claim 8 wherein said solvent contains from 0.25% to 10% water.

References ited in the file of this patent UNITED STATES PATENTS 2,909,576 Fenske et al Oct. 20, 1959 FOREIGN PATENTS 668,853 Great Britain Mar. 26, 1952 823,902 Great Britain Nov. 18, 1959 

1. A PROCESS FOR RECOVERING AN AROMATIC CONCENTRATE COMPOSED OF 2,6- AND 2,7-DIMETHYLNAPHTHALENES FROM CRACKED GAS OIL CONTAINING 2,6- AND 2,7-DIMETHYLNAPHTHALENES, WHICH COMPRISES CONTACTING AT A TEMPERATURE BETWEEN 240*F. AND 320*F. IN AN EXTRACTION ZONE CRACKED GAS OIL FEED CONTAINING DIMETHYLNAPHTALENES AND BOILING SUBSTANTIALLY WITHIN THE RANGE OF 400-650*F. WITH A POLYALKYLENE GLYCOL SOLVENT WHICH IS SELECTIVE FOR AROMATICS AND WHICH IS A SELECTIVE AZEOTROPE FORMED WITH DIALKYLNAPHTHALENES; SEPARATING A RAFFINATE PHASE RICH IN NONAROMATIC HYDROCARBONS AND AN EXTRACT PHASE ENRICHED IN DIMETHYLNAPHTHALENES; SUBJECTING THE EXTRACT PHASE TO AZEOTROPIC DISTILLATION; REMOVING AN OVERHEAD FRACTION CONSISTING ESSENTIALLY OF DIMETHYLNAPHTHALENES AND SOLVENT; RECOVERING 2,6- AND 2,7-DIMETHYLNAPHTHALENES FROM THE SOLVENT; AND REMOVING A BOTTOMS FRACTION CONSISTING ESSENTIALLY OF SOLVENT AND AROMATICS WHICH AZEOTROPE ABOVE SAID DIMETHYLNAPHTHALENES. 